Adhesive applicator

ABSTRACT

A device for dispensing liquid resinous material from solid rods includes a heated melting tube having a dispensing jet with a valve at one end, and a tapered insert at the other end made of a material to which the resinous material will not adhere. The drive feeding the rod into the insert is disengaged when the valve is closed and reengaged when the valve is opened. The arrangement prevents pressure build up when the device is stopped and limits back flow of molten material along the rod.

United States Patent [15] 3,653,552 Ash Apr. 4, 1972 [s41 ADHESIVEAPPLICATOR 3,337,093 8/1967 Newton ..222/146 HE 3,399,665 9/1968 Sprague..222/ 146 X [721 Invent Bernard Edwin Kent England 2,972,670 2/1961Dorosz et a1. ..219/19 ux [73] Assignee: International Standard ElectricCorpora- I "on, New York, NY Primary Examiner-Robert B. Reeves AssistantExaminer-Thomas E. Kocovsky Flledl 1969 Attorney-C. Cornell Remsen,.lr., Walter J. Baum, Paul W. 2 A L N 868 5 8 Hemminger, Percy P.Lantzy, Philip M. Bolton, lsidore Togut I] pp 3 and Charles L. Johnson[30] Foreign Application Priority Data [57] ABSTRACT Nov. 7, 1968 GreatBritain ..52,772/68 A device for dispensing liquid resinous materialfrom solid rods includes a heated melting tube having a dispensing jet[52] U.S. Cl. 222/146 HE, 126/343 A, 219/230, with a valve at one end,and a tapered insert at the other end 228/53, 401/2 made of a materialto which the resinous material will not ad- [51] int. Cl. ..B05c 5/02here. The drive feeding the rod into the insert is disengaged [58] Fieldof Search ..222/ 146; 18/30 FM, 30 F8, 30 OH, when the valve is closedand reengaged when the valve is 18/30 QZ', 219/230, 231, 421; 228/52,53; 401/1, 2; opened. The arrangement prevents pressure build up whenthe 126/3435 R, 343 A device is stopped and limits back flow of moltenmaterial along the rod. 56 R le nc s Cited 1 e N e 5Claims, 1 DrawingFigure UNITED STATES PATENTS 3,285,475 11/1966 Phillips ..222/146 11 A J6 I PATENTEDAPR 4 me lml r m 1 u me A, 0 o M M y E s B ADHESIVEAPPLICATOR BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to apparatus for dispensing resinous materials inliquid form when the resinous material is supplied in the form of acontinuous rod.

2. Description of the Prior Art Typically these resinous materials areadhesives which are required to be dispensed in the liquid form atprecisely controlled, but variable, rates. Known forms of dispensingapparatus suffer from two disadvantages. The rate of feed of the moltenmaterial is usually determined by the rate at which the rod of materialis fed into the apparatus, but when the apparatus has been running forsome time at a high rate of delivery and is then stopped by closing avalve at the dispensing end of the apparatus, the other end of theapparatus being blocked by the rod, there will be a pressure building upwithin thelapparatus as more of the rod becomes molten, most materialsexpanding on becoming molten. When the apparatus is restarted there willbe a sudden surge of molten material from the dispensing end because ofthe pressure build-up and this surge is frequently unacceptable.

In addition to this problem, there is the disadvantage that the supplyrod cannot be a tight fit in the entry end of the apparatus, which meansthat there is a tendency for molten material to creep back along thesides of the rod and escape from the apparatus. This can be overcome bykeeping the entry end of the apparatus below the melting temperature ofthe material, but in this case there is a tendency for the moltenmaterial to adhere to the inside of the entry end when the apparatus isstopped. If the resinous material readily adheres to metal aconsiderableforce will be required to restart delivery, which means that there willbe a variation in the rate of delivery.

SUMMARY OF THE INVENTION It is the object of the invention to provide adispensing apparatus which will not suffer from the aforementioneddisadvantages.

The present invention provides an apparatus for dispensing resinousmaterial in liquid form when the resinous material is supplied in theform of a continuous rod. The apparatus includes a melting tube,attached to one end of which is a dispensing jet containing a valve. Theother end of the tube includes a sleeve insert having a portion withsubstantially the same internal diameter as the external diameterof therod, and a portion with a tapered internal section, the taper increasingin section towards the jet end of the melting tube. The sleeve insert ismade of a material to which the resinous material will not adhere. Therod is fed into the melting tube at the sleeve insert end by a drivewhich is disengaged from the rod when the valve is closed and re-engagedwhen the valve is opened. An electrical heater extends over the meltingtube, except the portion containing the sleeve insert, the heatermaintaining the jet end of the melting tube at the dispensingtemperature of the resinous material, while the portion of the tubeadjacent to the sleeve insert is at the melting point of the resinousmaterial. The tube assembly is mounted at the sleeve insert end in alarge heat-conducting mass.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE shows the dispensingapparatus mainly in cross section.

DESCRIPTION OF THE PREFERRED EMBODIMENT The adhesive rod 1 of a suitableresinous material is fed into the apparatus by means of twofriction-drive wheels 2, which are driven at constant but variablerates. The rod melts in the melting tube 3, the molten material beingshown generally as 9, as the tube 3 is heated by the electrical heater4. At the inlet end of the tube 3 there is a polytetrafluoroethylenesleeve insert 5 having a tapered portion as shown as 8, the whole tubeassembly being mounted in a large metallic mass 6 as shown. The slidingvalve 7 cuts off the flow of adhesive from the jet 10 when the apparatusis stopped, jet 10 being heated by conduction from the tube 3 in orderto prevent the adhesive solidifying inside it.

The melting tube 3 is heated by the heater 4 in such a manner that itstemperature varies from the required application temperature at the jetend, to just above themelting point of the adhesive at the portion ofthe tube adjacent to the sleeve insert 5. The thickness of the tube 3around the sleeve insert 5 is kept to a minimum in order that there is aconsidera ble temperature gradient over the tapered section 8. Thistapered section 8 produces conditions whereby the molten material runsback along the rod 1 into a progressively narrowing gap, the sides ofwhich become progressively colder as the rod 1 feeds forward, whichcauses the molten material to freeze against the rod 1. The insert 5 ismade of polytetrafluoroethylene which is a material that the adhesivewill not adhere to, so that the rod cannot become adhered to the tubeentry when the apparatus is stopped, therefore the rod can be easilymoved forward when the apparatus is restarted.

When the apparatus is stopped, the sold material in the entry of tube 3melts and tends to force the supplying rod outwards due to the pressurebuilding up within the tube 3. The taper 8 in insert 5 is slight, and aspolytetrafluoroethylene is very flexible, the rod will not be restrictedfrom moving outwards by the taper 8 or the insert 5. If thefriction-drive wheels 2 are released from the rod when the apparatus isstopped, the rod 1 will be free to move outwards. If the heater 4 is nowswitched off the rod 1 will be drawn into the tube 3, by the contractionof the solidifying matter, which minimizes the risk of producing voidsin the material in the tube 3.

The apparatus is designed such that when it is switched off valve 7shuts, and at the same time the friction-drive wheels 2 areautomatically released from the rod 1, a suitable connecting mechanismbeing indicated by dashed line 11. The reverse procedure taking placewhen the apparatus is restarted.

The insert 5 may alternatively be made of material to which the adhesivewill not adhere.

What is claimed is:

1. An apparatus for dispensing resinous material in liquid form when theresinous material is supplied in the form of a continuous rod,comprising a melting tube having a passageway for said rod, a dispensingjet attached to one end of said tube, a valve controlling liquid flowthrough said jet, a sleeve insert having substantially the full lengthenclosed within the other end of the tube, said sleeve having an outerend portion of said passageway with substantially the same internaldiameter as the external diameter of the rod and an inner portion with atapered internal section enclosed within said tube, the taper increasingin section towards the jet end of the melting tube, the sleeve insertbeing made of a material relatively non-adherent to the resinousmaterial at temperatures cooler than at said jet end, means for feedingthe rod into the melting tube at the sleeve insert end, said means beingdisengaged from the rod when the valve is closed and reengaged when thevalve is opened, an electrical heater extending over the melting tubeexcept the portion containing the sleeve insert, said passageway withinthe electrical heater portion of said tube having a larger internaldiameter than that of said sleeve outer end portion to accommodate themelted rod material, said passageway having a constant internal diameterwithin said heater and tapering to a narrow diameter adjacent said jetend, the heater maintaining the jet end of the melting tube at thedispensing temperature of the resinous material while the portion of thetube adjacent to the sleeve insert is at the melting point of theresinous material, and a heat-conducting mass supporting said tube atthe sleeve end.

2. Apparatus as claimed in claim 1 wherein the resinous material is anadhesive.

3. Apparatus as claimed in claim 1 wherein the sleeve insert is made ofpolytetrafluoroethylene.

4. Apparatus as claimed in claim 1 wherein the means feeding the rodinto the melting tube comprises a pair of frictiondrive wheels andincluding means for automatically disengag ing said drive wheels fromsaid rod when said valve is closed and reengaging said wheels when saidvalve is opened.

5. Apparatus as claimed in claim 1 wherein the internal

1. An apparatus for dispensing resinous material in liquid form when theresinous material is supplied in the form of a continuous rod,comprising a melting tube having a passageway for said rod, a dispensingjet attached to one end of said tube, a valve controlling liquid flowthrough said jet, a sleeve insert having substantially the full lengthenclosed within the other end of the tube, said sleeve having an outerend portion of said passageway with substantially the same internaldiameter as the external diameter of the rod and an inner Portion with atapered internal section enclosed within said tube, the taper increasingin section towards the jet end of the melting tube, the sleeve insertbeing made of a material relatively non-adherent to the resinousmaterial at temperatures cooler than at said jet end, means for feedingthe rod into the melting tube at the sleeve insert end, said means beingdisengaged from the rod when the valve is closed and reengaged when thevalve is opened, an electrical heater extending over the melting tubeexcept the portion containing the sleeve insert, said passageway withinthe electrical heater portion of said tube having a larger internaldiameter than that of said sleeve outer end portion to accommodate themelted rod material, said passageway having a constant internal diameterwithin said heater and tapering to a narrow diameter adjacent said jetend, the heater maintaining the jet end of the melting tube at thedispensing temperature of the resinous material while the portion of thetube adjacent to the sleeve insert is at the melting point of theresinous material, and a heat-conducting mass supporting said tube atthe sleeve end.
 2. Apparatus as claimed in claim 1 wherein the resinousmaterial is an adhesive.
 3. Apparatus as claimed in claim 1 wherein thesleeve insert is made of polytetrafluoroethylene.
 4. Apparatus asclaimed in claim 1 wherein the means feeding the rod into the meltingtube comprises a pair of friction-drive wheels and including means forautomatically disengaging said drive wheels from said rod when saidvalve is closed and reengaging said wheels when said valve is opened. 5.Apparatus as claimed in claim 1 wherein the internal diameter of saidmelting tube is enlarged in the section extending around said sleeveinsert to provide a temperature gradient over said tapered sleeve, theexternal diameter of said tube being constant along said sleeve insertportion and said heater portion.